Conventionally, disturbance signals such as noise components and echo components included in an acoustic signal have been reduced by using a digital signal processor (DSP), for example. In the DSP, a noise canceller and an echo canceller change characteristics of the acoustic signal to reduce such disturbance signals. A technique using a plurality of microphones (a microphone array) has been proposed for reducing disturbance signals such as noise components and echo components included in a picked-up sound signal obtained by the microphone array and outputting the resulting signal as an output signal. For picking up sound by using a plurality of microphones, a technique (an utterer tracking microphone array) has also been proposed in which directivity of the microphones is directed toward a user who utters, and disturbance signals such as noise components are reduced by adaptively changing the directivity.
When the utterer tracking microphone array for picking up sound and a plurality of loudspeakers for outputting acoustic signals are used together, the directivity for picking up sound changes as a user moves in a space to which the acoustic signals are output. As a result, loudspeakers causing an echo are shifted according to the location of the utterer. The conventional technique, however, cannot effectively reduce the disturbance signals generated in relation to the location of the user because a relative direction (relative position) between the user and the loudspeakers is not taken into consideration to reduce the disturbance signals.